Pelosi had been scheduled to appear alongside Gore at a press availability after a meeting of the House Democratic Caucus this afternoon, but a source in the Speaker's office said Pelosi thought it would be more effective to have Gore on the phone calling lawmakers one-on-one.

Pelosi surprisingly scheduled the American Clean Energy and Security (ACES) bill for a vote this week, exuding confidence that the landmark climate change bill would receive enough support to make its way through the House.

Republicans have derided the bill, also known as "Waxman-Markey" for its authors, as amounting to a de facto tax on energy consumption.

Gore is a former Democratic presidential candidate in 2000 whose environmental activism had earned him a Nobel Peace Prize and an Academy Award.